In my opinion, you'd be as well being employed directly by the agency. You're paying them for the privilege of being paid by them.

Hummm... It was the Agency who recommended them so I doubt they do direct employment. The contract is for min of 1 month so its not too bad unless it gets extended, which is highly likely.

Are you likely to earn enough that Ltd Company becomes a valid option? Obviously don't answer that, just think about it.
The agency probably recommend an umbrella company cos it absolves them from any kind of extra work re: employee national insurance, pensions, etc., etc., etc. They just receive an invoice from the umbrella company and and pay it.

My mate has his own LTD company but he's been doing it for years and doesn't recommend it if I'll be short term because its "a bit of a ball ache".

I suppose I should just suck it up and then see what happens in 4 weeks